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NASA Sends Spacecraft on Mission to Comet Hartley 2

12.13.07

This is an artist concept of Epoxi, which uses the Deep Impact spacecraft. Image credit: NASA/JPL› Full image and caption
NASA has approved the retargeting of the Epoxi mission for a flyby of
comet Hartley 2 on Oct. 11, 2010. Hartley 2 was chosen as Epoxi's destination
after the initial target, comet Boethin, could not be found. Scientists
theorize comet Boethin may have broken up into pieces too small for detection.

The Epoxi mission melds two compelling science investigations -- the Extrasolar
Planet Observation and Characterization and the Deep Impact Extended Investigation.
Both investigations will be performed using the Deep Impact spacecraft.

In addition to investigating comet Hartley 2, the spacecraft will point the
larger of its two telescopes at nearby previously discovered extrasolar
planetary systems in late January 2008. It will study the physical properties
of giant planets and search for rings, moons and planets as small as three Earth
masses. It also will look at Earth as though it were an extrasolar planet to
provide data that could become the standard for characterizing these types of planets.

"The search for exosolar planetary systems is one of the most intriguing explorations
of our time," said Drake Deming, Epoxi deputy principal investigator at NASA's Goddard
Space Flight Center, Greenbelt, Md. "With Epoxi we have the potential to discover new
worlds and even analyze the light they emit to perhaps discover what atmospheres
they possess."

The mission's closest approach to the small half-mile-wide comet will be about nearly a
thousand kilometers (620 miles). The spacecraft will employ the same suite of two
science instruments the Deep Impact spacecraft used during its prime mission to guide an
impactor into comet Tempel 1 in July 2005.

If Epoxi's observations of Hartley 2 show it is similar to one of the other comets that
have been observed, this new class of comets will be defined for the first time. If the
comet displays different characteristics, it would deepen the mystery of cometary diversity.

"When comet Boethin could not be located, we went to our backup, which is every bit as
interesting but about two years farther down the road," said Tom Duxbury, Epoxi project
manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Mission controllers at JPL began directing Epoxi towards Hartley 2 on Nov. 1. They commanded
the spacecraft to perform a three-minute rocket burn that changed the spacecraft's velocity.
Epoxi's new trajectory sets the stage for three Earth flybys, the first on Dec. 31, 2007. This
places the spacecraft into an orbital "holding pattern" until it's time for the optimal encounter
of comet Hartley 2 in 2010.

"Hartley 2 is scientifically just as interesting as comet Boethin because both have relatively
small, active nuclei," said Michael A'Hearn, principal investigator for Epoxi at the University
of Maryland, College Park.

Epoxi's low mission cost of $40 million is achieved by taking advantage of the existing Deep
Impact spacecraft.